FIG. 1 illustrates a conventional digital cellular telecommunications systems, namely, the system conventionally known as the Personal Digital Cellular (PDC) system. One feature of this system is to provide Internet connectivity to mobile stations using the conventional RCR 27 Standard, which is incorporated herein by reference. Data transfer for Internet connectivity in the system of FIG. 1 is based on the Internet Protocol (IP), that is, the packet data transmission model is implemented end-to-end, including the air interface. The example of FIG. 1 represents one way to implement the network structure for PDC packet and circuit services.
In FIG. 1, the Visited Mobile Services Switching Center (VMSC) and the Gateway Mobile Services Switching Center (GMSC) implement the circuit based services to the Public Switched Telephony Network (PSTN) or to the Integrated Services Digital Network (ISDN). VMSC also implements the circuit based functions related to the Control Channel (CCH) towards the mobile station (MS). One example of such functions, location registration, is used to update the location of the mobile station MS to the Home Location Register (HLR).
The Visited Packet Mobile Services Switching Center (VPMSC) and the Gateway Packet Mobile Services Switching Center (GPMSC) implement the packet data services. VPMSC controls the User Packet Channel (UPCH) towards the mobile station MS and it also implements the mobility functions for the mobile station while the mobile station is in packet mode. GPMSC controls connections toward the Internet.
The network also contains nodes for specific functions. For example, the Short Message Services Center (SMSC) implements short message storage and delivery functions for the Short Message Service (SMS). SMS uses the ISDN User Part (ISUP) for signaling within the mobile network in generally the same way that it is used for establishing normal speech calls. The SMSC can also be connected to the Internet, which makes it possible to use E-mail for providing Short Message Service to the mobile station.
In FIG. 1, when the mobile station is using Internet services, the mobile station MS communicates with the base station BS and VPMSC through the UPCH. This means that the mobile station is essentially locked to UPCH, and therefore cannot monitor other channels such as the paging channel on CCH. The packet session is further connected via the internal backbone and GPMSC to the Internet.
If the mobile station receives a speech call from PSTN while the mobile station is using Internet services (i.e., during a packet session), then GMSC receives the speech call from PSTN and interrogates HLR for the location of the mobile station. HLR has information about the mobile station location and also has information indicating that the mobile station is in packet mode. That information is returned to GMSC, so that GMSC can reroute the call to VMSC, in whose service area the mobile station is currently located.
Because the mobile station is in packet mode, there is no need for VMSC to page the mobile station on CCH. Therefore, VMSC orders VPMSC to send the paging order on UPCH. If the subscriber using the mobile station accepts the incoming speech call, then the mobile station sends this acceptance on UPCH. The mobile station then closes the current packet session, and establishes a connection on traffic channel TCH to receive the incoming speech call.
Conventionally, when the mobile station is in the packet mode, the mobile network handles an incoming short message similarly to an incoming speech call. In this case, and referencing also FIG. 2, the short message is received in SMSC, which then calls GMSC (20). GMSC then interrogates HLR (21) to obtain the latest information about the mobile station. GMSC then calls VMSC (22). If (23) the mobile station is not in packet mode, then CCH is used to provide the Short Message Services. If (23) the mobile station is in packet mode, VMSC calls VPMSC (25), and VPMSC pages the mobile station on UPCH (26).
Because the mobile station is in the packet mode and therefore monitoring UPCH, the user of the mobile station can accept the incoming call and agree to receive the incoming short message. Similarly to the situation described above with respect to the speech call, the mobile station closes the packet session and establishes a connection on CCH in order to receive the short message (27). VMSC then sends the short message on CCH using the layer 3 protocol of the conventional OSI protocol stack (28).
The above-described conventional techniques have the following disadvantages. Because the short message includes only textual information, it is quite inefficient to force the mobile station to move from UPCH to CCH to receive the short message. To close the packet session, the user will generally have to terminate the session to Internet before accepting the incoming call. Moreover, at the time that the incoming call is accepted, the user does not even know that the incoming communication is a short message, which can, of course, be stored and read later without requiring the user to close the current packet session. For example, because the user might not want to take the risk of missing a speech call, the user may interrupt and close the packet session to accept a call (textual message) that could have waited until the user had finished the packet session. Also, the process of closing the packet session and establishing the connection to CCH to receive the short message (and the subsequent reopening of the packet session) disadvantageously requires a significant amount of signaling between the mobile station and the network.
Other conventional systems use an Internet service, such as E-mail, for sending all short messages to the mobile subscriber. The SMSC transfers all SMS messages to the E-mail application. Although such systems do not give rise to the aforementioned disadvantages, nevertheless, circuit switched Short Message Service is typically more appropriate for sending short messages because it usually will provide the message to the intended party in a more timely fashion than will E-mail.
It is therefore desirable to provide Short Message Service that avoids the aforementioned disadvantages.
The present invention avoids the aforementioned disadvantages by using the packet channel to deliver SMS messages, but only if the mobile station is already in the packet mode.
The present invention also avoids the aforementioned disadvantages by using the layer 3 protocol of the OSI protocol stack to transmit SMS messages over the packet channel.